Many types of machines have been devised for sewing quilts, comforters and the like. Many conventional sewing machines may be adapted to quilting by placing them on rollers or tracks on a quilting frame so that the operator may move a needle of the sewing machine in a pattern while keeping the quilting materials stationary.
If a quilting apparatus is equipped with a conventional sewing machine without modification, problems are encountered because of the thickness of the material to be quilted. In particular, quilts incorporate at least three material layers: two outer pieces and a filler material inbetween. The filler material may be thin or thick, depending upon the final use of the quilted product. Therefore, a problem often experienced is the inability of the traditional presser foot utilized on most sewing machines to adjust to different quilt thicknesses, causing erratic feeding of the material and thus unwanted variable stitch lengths.
Furthermore, such a conventional presser foot normally places constant pressure against the material and tends to bunch or gather material together when used in a quilting process where stitching is rarely in a straight line.
Other problems resulting from using a conventional sewing machine as part of a quilting machine are associated with the tension mechanism. Because quilts are usually fairly large and require a substantial length of stitching thread, it is advantageous to use a large bobbin in order to reduce the number of bobbin thread changes. If the thread being used for the quilting is heavy weight and the mechanism is run at a low speed, the use of a large bobbin does not cause much of a problem. But when lighter weight threads are used and/or the operator attempts to run the sewing machine at a high speed, thread breakage and undesirable thread looping often occur because the tension on the thread coming from the large bobbin is greater than the tension placed upon the thread coming through the needle. When the top thread coming from the needle has more slack than the bottom thread from the bobbin, a loop is formed by that top thread on the underside of the material during the final tightening of the stitch. Besides being unsightly, the looping of the top thread creates a less than adequate hold or knot with the bobbin thread, allowing the bobbin thread to slip as successive stitches are made, sometimes causing the bobbin thread to break under this added stress. It is, therefore, desirable to have a sewing machine with special material controlling mechanism and thread tensioning mechanism when used to make quilts.
In particular, a material controlling mechanism that is especially advantageous for use with a quilting machine includes a presser foot that reciprocates in coordination with the reciprocating needle, pressing against the materials as the needle makes a stitch, then lifting as the material controlling mechanism is moved to the position of the next stitch.
Many of the quilting machines that use a reciprocating or "hopping" presser foot do not utilize a traditional sewing mechanism to do the quilting. The mechanism used is often large and stationary, having several needles and presser feet and having material to be quilted fed therethrough. Therefore, the hopping feet are often part of a complicated feed bar system.
Other hopping foot mechanisms have been created for use with sewing machines that do not necessarily sew quilted materials. Such mechanisms frequently include intricate and sometimes elaborate arrangements of joints and levers which allow the foot to adjust for different material widths, but are often expensive and require careful maintenance.
Intermittent tension devices have been used in a variety of sewing applications where extra tension is needed. Multi-thread intermittent tension mechanisms are used to embroider fabric, placing tension on certain threads at certain times during the embroidery process in order to sew a desired color of thread. Intermittent tension devices have also been used in sewing heavy materials or materials with a hard finish, such as denim or canvas, so that very heavy tension is applied on the thread at the final tightening of the stitch. However, suitable tension devices have not been provided for quilting mechanisms as described herein so that heavier tension may be placed at the final tightening of the stitch to balance the already heavy tension on the bobbin thread.
In particular, conventional intermittent tension mechanisms commonly function by interraction with an eccentric cam located on a cross drive shaft of the sewing machine. In many of the mechanisms, the thread is held tightly between two disks biased together by a spring. A rod connected to the eccentric cam, reciprocates, pushing at one point in its cycle against the outer tension disk and the spring, relieving tension on the thread. This type of system works well for embroidery where the thread must be held in place until a certain point in the sewing cycle when it is allowed to pass through the mechanism and be used to make a stitch. However, such mechanisms do not work as well in applications wherein it is desirable to apply a certain thread tension until one point in the sewing cycle after which additional tension is required to complete the cycle.
Another problem often encountered with intermittent tension devices is that the reciprocating rod rubs against the eccentric cam. With continuous use, friction between the rod and cam produces wear on both parts, resulting in improper tension and requiring replacement of worn parts. Also, any type of connection between the rod and cam that is left open to the environment is problematic because of lint build up caused by the materials to be sewn. This is particularly a problem with quilting due to the loose consistency of the inner filler material.